[CREATE] W3C Compositing and Blending 1.0 draft is up: implications for OpenRaster?

[Guillermo Espertino (Gez)]

El 12/11/12 12:50, Andrew Chadwick escribió:
> Correction to my statements upthread: I think the practical answer is:
> blend in device space (!), or if you want to be more predictable, blend
> in nonlinear sRGB.
>
> FWIW, Photoshop seemingly does the blending non-linearly in indexed RGB
> mode, looking at the examples at http://dunnbypaul.net/blends/ and
> recreating them in MyPaint master HEAD=5d100ff5 (which uses nonlinear
> sRGB space for blends). Results using the two sample images are
> identical, modulo dithering.

As far as I can remember (I haven't used photoshop for four years) there 
was an option to select the gamma for blending.
I can't remember what was the default, but I think it was 1.0, which 
would mean that Photoshop blends in linear space as default.

> I'm not sure how things are supposed to be *composited* though. The
> above quote doesn't answer that. I would still very much like this to be
> linear :/ Perhaps you're still supposed to be explicit about compositing
> space in SVG.

Every high end application out there seems to use linear, plus it's 
quite easy to see the nasty effects of blending in nonlinear.
I don't know if there's a good reason behind keeping nonlinear blending, 
although just blending images together without caring about their 
colorspaces, assumming their gamma is 2.2 sounds like a less intensive 
task than linearizing, blending and gamma correcting back.
I'm not sure if this is still relevant today, but seemed like a 
reasonable question to ask. :-)

Thanks for the feedback.
Gez.